Police have arrested two people in relation to a racist and sexist tirade on a French tourist aboard a Melbourne bus but say they are still looking for a man who instigated the verbal attack.

The pair, from Hampton Park, have been released without charge.

A police spokeswoman said a 24-year-old man and 21-year-old woman had been released pending further inquiries.

The French woman was called a c---, a dog and threatened with having her breasts cut off after she sang a song in her native language on the bus between Mordialloc and Caulfield on November 11.

The incident, filmed by Melbourne comedian and bus passenger Mike Nayna, sparked outrage here and overseas after it went viral on YouTube.

A police spokeswoman confirmed a formal complaint had been made to police, and another passenger had provided them with video of the incident.

A couple pushing a pram, who are believed to be the pair arrested and then released by police, can be seen abusing the woman, with the man shouting: "I'll f---ing boxcutter you right now, dog" before both disembarked.

Investigators are seeking further assistance to identify others in the footage. One is a man, who is described by police as having a red face and dirty blonde hair, but is yet to be identified.

Police could charge those responsible for the incident with assault or language related offences, and racial vilification.

In 2010, three men were the first in Victoria charged with inciting racial hatred, accused of verbally and physically assaulting an Indian man on a bus between Frankston and Rye. All three had charges against them dropped last year.